An electro-absorption (EA) modulator holds distinct advantages over the silicon Mach-Zehnder interferometer (MZI) modulator by having lower energy consumption, a smaller footprint on-chip, and a potentially higher modulation speed. These are crucial for efficient encoding of optical signals in silicon photonics circuits. Furthermore, the development of a Group IV-based (i.e. silicon- or germanium-based) EA modulator allows compatibility with standard complementary metal-oxide-semiconductor (CMOS) processing. In this work, we demonstrate a novel evanescent germanium (Ge) EA modulator structure. A lateral electric field is employed in the Ge rib to enhance absorption via the Frank-Keldysh effect. This shifts the absorption edge significantly with applied bias for wavelengths beyond 1600 nm. A peak extinction ratio of ~15 dB at 1600 nm could be achieved for a <3 V dynamic voltage swing from a 20 μm modulator. The impact of device dimensions and design structure on optical modulation and insertion loss are also investigated. In addition, monolithic integration of waveguided Ge-based modulator and photodetector can be simplified with our proposed EA modulator structure. The results from this work can make a low power and high speed Ge-based EA modulator viable for future silicon photonics applications.

Date Published: 17 May 2010
PDF: 8 pages
Proc. SPIE 7719, Silicon Photonics and Photonic Integrated Circuits II, 77191Z (17 May 2010); doi: 10.1117/12.854089

Published in SPIE Proceedings Vol. 7719:
Silicon Photonics and Photonic Integrated Circuits II
Giancarlo Cesare Righini, Editor(s)